President Barack Obama and his family are expected to fly to Kennedy Space Center for today's Endeavour launch. The Arizona congresswoman arrived Wednesday and will watch her husband take off into space from a private location.

At 3:47 p.m., Endeavour is expected to thunder into the sky.

There's a 70 percent chance it will leave as planned, NASA officials said Thursday.

Giffords' husband, Navy Capt. Mark Kelly, will lead the six-man shuttle crew to the International Space Station. During the 14-day mission, they'll deliver supplies, including the Alpha Magnetic Spectrometer-2, a particle detector that scientist hope will detect dark matter and antimatter.

Endeavour is the next-to-last launch before NASA's shuttle program winds down. The space shuttle Atlantis is expected to launch on June 28.

Though all the tickets for on-base viewing of Endeavour's launch were snatched up long ago, there are other popular viewing spots:

Beware: Authorities say the expected crowds could rival those of the most-attended launches in history. Some officials estimate that between 500,000 to 750,000 will descend upon the Space Coast.

So there's always the other option:

At 3:47 p.m., look east.

Information from Times wires was used in this report. Jessica Vander Velde can be reached at jvandervelde@sptimes.com or (813) 226-3433.

Poignant presence, but out of view

Since Rep. Gabrielle Giffords' arrival, her whereabouts have been kept secret. A staff member said in a Twitter update Thursday morning that Giffords, who survived an assassination attempt Jan. 8 at a political event in her Tucson, Ariz., hometown, was enjoying Florida and "all the space action." She will watch the launch in the general area of the presidential entourage, and her staff says there are no plans to release photos of her.